Amides and process of preparing same with a monocarbodhmide



United States Patent C AMllDES AND PROCESS OF PREPARING SAME WITH A MONOCARBODHIVIDE John C. Sheehan, Cambridge, Mass, assignor to Arthur D. Little, Inc., Cambridge, Mass, a corporation of Massachusetts No Drawing. Filed Oct. 10, 1958, Ser. No. 766,406

22 Claims. (Cl. 260-112) The present invention relates to the formation of peptide and other amide linkages, to the chemical agents which facilitate the formation of such linkages and to the treatment of protein and peptide materials with such agents.

This application is a continuation-in-part of United States application Serial No. 641,853, filed February 25, 1957, now abandoned, which, in turn, is a continuationin-part of Serial No. 551,331, filed December 7, 1955, now abandoned, for Product and Process.

It has now been found that peptides and other amide linkages may be formed readily in the presence of an aliphatic carbodiimide. The aliphatic carbodiimides of the present invention have the general structure in which at least one aliphatic carbon atom is attached to one of the nitrogen atoms of the --N=C:N- structure. Such aliphatic radicals may be cyclohexyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, iso-butyl, tertbutyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, benzyl, ozand fl-phenylethyl, ethyl morpholinyl, diethylaminoethyl, ethylpiperidyl, 11-, ,8- and 'y-methylor ethylpyridyl.

The carbodiimides of the present invention may be prepared in accordance with the general method of E. Schmidt, F. Hitzler and E. Lahde, Ber. 71, 1933 (1938), from the corresponding thioureas by oxidation with mercuric oxide in acetone. The thioureas may be prepared from the corresponding amine by reaction with carbon disulfide in the case of symmetrical thioureas. The unsymmetrical thioureas may be prepared by interaction of an amine with an isothiocyanate. The carbodiimides are also preparable from the corresponding ureas, and are regeneratable after use, thus permitting recycling of the condensation agent, following the procedure of Amiard, G. and Heymes, R., Bull. Soc. Chim.; France, 1360 (1956). I

Of the carbodiimides of the present invention those most preferred are the water-soluble carbodiimides since the most useful applications of the process involve the use of aqueous media either during amide formation, or in the purification of the amide or in the separation of the resulting urea which may, if desired, be regenerated to carbodiimide and reused. Carbodiimides bearing tertiary amino groups may be rendered soluble in water by neutralizing said amino group with an acid capable of forming a substantially neutral salt with the tertiary amine. Such acids include the hydrohalic group, hydrogen chloride, hydrogen bromide and hydrogen iodide, sulfuric acid, sulfonic acids, nitric acid, phosphoric acid, phosphonic acids but ordinarily do not include carboxylic acids since the latter place in the carbodiimide a carboxyl group which provides a carboxyl group as the reactant-in combining with the amino group of the other reactant to form an amide linkage. Also, carbodiimides bearing tertiary amino groups may be rendered water soluble by quaterm'zation with methyl p-toluenesulfonate (methyl boxylic acid and quaternary ammonium base groups are examples of groups that are often too acidicor basic to be employed directly in the carbodiimides of the present invention. a

As is evident to those skilled in the art the reaction shown in the accompanying detailed examples involves the condensation of a primary or secondary amino group and a carboxyl group with the elimination of a molecule of water and formation of an amide bond. This water is picked up by the carbodiimide, preferably monocarbodiimide, resulting in conversion of the carbodiimide to the corresponding urea. This reaction is illustrated by the following general equation in which only the functional groups involved are shown:

This reaction occurs readily under mild conditions of temperature with a high degree of selectivity providing high yields and a minimum of side reactions and resultant by-products which would require extensive purification. The reaction can be carried out in a wide ,variety of solvents ranging from completely organic media such as dioxane, tetrahydrofuran, methylene chloride, acetonitrile, benzene, ethyl acetate, hexane, acetone, formamide, dimethyl forrnamide with and without lithium chloride to aqueous. systems including water alone or with acetone, dioxane, tetrahydrofuran, acetonitrile and the like. With the instant water-soluble carbodiimide condensing agent, it is also practical to use organic solvent during the amide formation and aqueous systems for subsequent purification and removal of the urea and un-v changed carbodiirnide. The term water soluble as used, in the specification and claims with reference to carbodiimide refers to carbodiimides having a solubility in water to an extent of at least 0.01% by weight and preferably at least 0.1% by weight. Pressure has not been shown to be a factor. No catalysts havebeen found to offer any advantage, nor have the concentration of reactants and carbodiimide been shown to be critical. Of. course, it is best to employ equimolecular proportions of reactants in the usual case although when carrying out the reaction in aqueous, alcoholic or other possibly re active media it is advantageous to employ an excess of the carbodiimide reactant.

While the bonds formed in the examples are generally described as peptide linkages it will be recognized that the carbodiimides of the present invention are equally applicable to the formation of amide bonds generally. The functional groups involved in the reaction are the same whether protein, amino acids, peptides or non-peptide reactants are employed and the linkage or grouping produced, CO-N-, is the same. This is shown, for example, in the polymerization of adipic acid and hexamethylenediamine which proceeds through the formation of amide bonds. using the carbodiimides of the present invention under mild conditions of temperature.

condensing agent efiects the formation of an amide by -such as N-allylaniline,

condensing'an amine containingan amino group, capable of being acylated and having at least one hydrogen attached to the amino nitrogen; with an organic carboxylic acid capable of forming amide bonds.

In accordance with the accompanying detailed examples, the reaction is efiected between carboxylic'acids and ammonia, primary and secondary amines; illustratively, primary aliphatic amines; such as, for example, methylamine, ethylamine, propylamine, butylamine, hexylamine, allylamine; secondary aliphatic amines, such as, dimethyl amine, diethyl amine, dipropylamine, dibutylamine; substituted aliphatic amines, and aralkylamines; such as chloroethylamine, phenethylarnine, benzylamine; aryl amines, aniline, 'alphanaphthylaminef betanaph thylarnine; substituted arylamines, m-toluidine, p benzylaniline; secondary mixed aliphatic-aromatic -am-ines,

benzylaniline; cyclic amines, piperidine, morpholine; heterocyclic amines, aminopyrimidine; diamines, butylenediamine, and e hylcnediaminc The acids suitable for reaction in the instant-amidfcirma; tion are organic carboxylic acids, capable of formingan amide withan amine,illustratively, aliphatic'acidsfac'etic, propionic, butyric, lauric, oleic,- glycollic, citric; lactic, glutaric; 'maleic, succinic, dime'thylacetic, heptanoic,-betacyclopentylpropionic, cholic, rnonochloracetic, dichloracetic, trichloracetic, acetoacetic, beta-acetylpropionic; aryl acids, benzoic, Z-methylbenzoic, Z-methoxybehzoic, salicyclic; parahydroxybenzoic, para-aminobenzoic, aral kylacid, betanaphthoic, phthalic; phenylacetic, cinnamic, betaphenylpropionic; heterocyclic acids, furoic and betapyridinecarboxylic. In the event that-cysteine is selected for condensation with amine by the instant process, it is desirable that the sulfhydryl group be first blocked by benzylation. As recognized in the art, where reactive side'chain substituents occur, and if desired, are to be protected, they may be blocked, in the case of amino by carbobenzoxylation, carbonyl by esterification to methyl or benzyl esters, and hydroxyl by acetylation or carbobenzoxylation. 1

Reaction of amines and acids to form amides are of course most readilyefiected in the solution state, however amino groups available for the reaction so that no pretreatment'for this purpose is required. These are gener-- ally regarded as being provided principally by the terminal amino group of lysine. Such side amide groups are supplied by glutarnic and aspartic acid units in the protein structure. Swelling, softening, penetrating or surface active agents can be employed to increase depth of effect.

Protein fibers such as hair, furs, silk, wools and the like, may be treated with the carbodiimides of the present invention to impart dimensional stability, including-re sistance to shrinking, hardness, increased tensile strength and the like. This treatment of fibers can also beprcceded' advantageously bysuch pretreatments as those described above in connection with hides.

Both hides and animal fibers canbe treated in accordance with the invention to increase water repellency or resistance and wet strength; In such a case softening either the amine or the acid may be undissolved or in a different phase and reactions are eflected between undissolved solids functioning as acids and aminesas illustrated by the treatment of wool, felt and'leather with carbodiimide in accordance with this invention,

.The carbodiimides of the present invention'may' be employed in the treatment of protein materials such as animal 'hides,,animal fibers, polypeptide fibers such as furs and' hair, feathers, casein, zein, soy prosilk, wools, tein, gliadin, egg albumen, lactalbumen, gelatin, and the like. Theuse of the carbodiimides to form amide bonds' has the general effect of increasing the molecular size, ofv the protein treated whether it be. that contained in hides, furs, feathers orthe extracted protein such as casein, albumens, .zein, gelatin and the like. This increase in mof lecular weight usually involves .the' form'ationof cross linkages, especially in the case of the fibrous proteins although to a lesser extent in the case of the globular proteins. (In the treatment of proteins withcarbodiimide in accordance with this invention, it is now practical to avoid, if desired, the introduction of new reactants into the protein and at the same time the, proteins are modified but retain their characteristic antigenicity. Thus virus cultures and bacteria are completely inactivated bycarbodiimide'but show the characteristic antigenicity of their: native protein upon injection ;into an animal.

Advantage can be taken of these generalefiects in the treatment of hides to cause hardening or tanning. In such av case no fragment is left in the hide as in the case of'using chrome'alum, tannin, formaldehyde and like agents employedtoday. Such treatment with a carbodi-- imide is usually desirably preceded by a treatment designed to, make available an increased number of carboxyl groupsi In most cases there are an adequate number of metallic salts (chrome alum) and include a lysine' content or swelling'pretreatment ofierslittle advantage but treatment to' provide an increasednumber of free carboxyl groups at the surface of-thc hide or fiber iis advantageous. It is also possible as indicated above to treat extracted proteins such as casein, zein, gliadin, soy protein, soy

albumen, egg albumen, lactalbumen; gelatin and the like.

In the'case of casein the result is the formation 'of-high polymers useful in the production of molded or extruded plastic articles or in paints where enamel or hard surfaces are desired. In thecase of gelatin the carbodiirnides of the present invention may be used-to increase molecular weight of jellying power usually expressed in terms of Bloom and they may also be used to harden or otherwise modify the gelatin for photographic purposes, e.g., a

5% solution of gelatin invwater to which was added an amount of l-cyclohexyl-S-[2-morpholinyl-(4)-ethyl] car bodiimidc metho-p-toluene-sulfonate equal in weight to the gelatin set to a gel in'SO seconds and after 13 minutes had hardened to the point where it could not be melted at steam-bath temperatures.

The gelatin of this'invention is readily distinguishable from collagen or gelatin, as heretofore known. Collagen is not water-soluble'as compared with gelatin. Both collagen and prior art gelatin contain lysine in combined form as part of the protein, but with free aminonitr'ogen, principally -amino, analysis of about 0.64 percent. Dearninated gelatin in which the amino groups have been removedand the amino acids thus altered are known. The instantfully modified gelatin contains all of its orig inal' amino acid content but with no added residues derived from conventional hardening agents; such as, for example, aldehydes (formaldehyde or glyoxal) and of about 4 percent, but with a Van Slyke free'aminonitrogen analysis of less than about 95 percent of the Van Slyke free amino-nitrogen analysis of the correspondmg untreated gelatin. This modified gelatinwhich has a Van Slyke free amino nitrogenanalysis of about 95 percent less than the Van Slyke free amino-nitrogen analysis of, the corresponding untreated gelatin possesses increased viscosity in aqueous dispersion and is productive of higher melting point gels at a particular concentration than is effected with ordinary gelatin. A lower. viscosity modified gelatin, without having a reduction in molecular weight or degradation, is effected by the modified gelatinshaving a Van Slyke free amino-nitrogen analysis, of less than about 25 percent of the Van Slyke free amino-nitrogen analysis of the corresponding untreated gelatin. Thus,

1 substantially all of the free amino group content and carparticular melting point or other desired-property, The

degree of: modification of the gelatins modified by'this aces sea invention may be determined, in addition to a Van Slyke free amino-nitrogen content before and after modification, by reaction with 2,4-dim'tro fluorobenzene (Sangers reagent) followed by total hydrolysis and measurement of free lysine. Thus, the modified gelatin having a Van Slyke free amino-nitrogen analysis of less than about 95 percent of the Van Slyke free amino-nitrogen analysis of the corresponding untreated gelatin, when so tested, has an acylated lysine e-amino content of about percent.-

-The carbodiimides of the present invention not only provide increased molecular weight by linear combination or end to end linkages to increase the length of the protien molecule, but the carbodiimides also serve to cause cross linking between adjacent protein chains. It is particularly advantageous that the carbodiimides provide both types of linking since this, in turn, provides maximum effect with respect to tanning hides, fixing fibers, hardening proteins and the like.

The carbodiimides of the present invention may be employed in the preparation of pharmaceutical or biologically' active compounds or materials. For example, gramicidinS, which is a macrocyclic peptide antibiotic containing ten amino acid units in a thirty-membered ring, could be prepared using the carbodiimides both in building up the ten amino acid unit chain and in the final cyclization. Similarly, peptide hormones such as those of the pituitary gland termed vasopressin and oxytocin may also be prepared using the carbodiimides of the present invention.

In accordance with this invention directed to the formation of amide linkages as described in detail, those having particular utility are the water-soluble aliphatic carbodiirnides. These and their preparation have been exemplified. They are novel and possessed of especial advantage in that the amide linkages may be formed in aqueous media and most amino acids, peptides and proteins are most soluble or compatible in such media. Also, such carbodiimides result in water-soluble ureas which are most easily removed from the reaction mixture or otherwise separated from the product containing the newly formed amide linkage. Surprisingly, such carbodiimides dehydrate the carboxyl and amino groups involved in the reaction and do so in aqueous media.

Detailed procedures for preparing carbodiimides typical of those of the present invention are set forth below:

Example I A portion was recrystallized from acetone-ligroin, M .P. 128-129 C.

1 -cyclohexyl-3- [Z-m orpholinyl- (4 -ethyl carbodiimide. -A mixture of 40 g. (0.0147 mole) of 1-cyclohexyl-3- [2-morpholinyl-( 4) -ethyll thiourea and 6.0 g. of mercuric oxide (Merck yellow) in 50 ml. of acetone was heated (magnetic stirrer) under reflux for 6 hours. The mercuric sulfide formed, was removed by filtration, a second 6 g. portion of mercuric oxide was added, and the suspension was heated at reflux for another 6 hours. The reaction mixture was again filtered and the filtrate concentrated. under reduced pressure. The oily residue was evaporatively distilled at 140 C./O.2 mrn.; yield 2.4 g. (70% Analysis.-Calcd for C H N O: C, 65.78; H, 9.77; N. 17.71. Found: C, 65.60; H, 9.59; N. 17.71.

Example 3 1 cyclohexyl 3 [2 morpholinyl (4) ethyl] carbodiimide metho-p-toluenesulf0naIe.-A mixture of 0.5 g.

Example 4 1-cyclohexyl-3-(4-diethylaminocyclohexyl) thiourea- After heating under reflux for 15 minutes a solution of 5.0 g. (0.029 mole) of N,N-diethyl-1,4-cyclohexyldiamine and 4.2 g. (0.03 mole) of cyclohexylisothiocyanate in 10 ml. of ether was evaporated under reduced pressure. Crystallization of the residue from warm ligroin and recrystallization from an acetone-ligroin mixture afforded 7.2 g. M.P. 139-141 C., of the pure thiourea.

Analysis.-Calcd. for C H N S; C, 65.59; H, 10.61; N, 13.50; S, 10.28. Found: C, 65.65; H, 10.66; N, 13.60; S, 10.36,.

Example 5 1-cycl0hexyl-3 (4 diethylaminocyclohexyl) carbodiimide.--A suspension of 2.0 g. of mercuric oxide in 20 ml. of acetone containing 0.8 g. (0.003 mole) of l-cyclohexyl-3-(l-diethylaminocyclohexyl) thiourea was refluxed for 20 hours. The mercuric sulfide formed was removed by filtration, the filtrate was concentrated under reduced pressure, and the residue was evaporatively distilledat 140 C./0.03 mm., 0.6 g. (84%).

Analysis.Calcd. for C H N C, 75.59; H, 11.26; N, 15.15. Found: C, 73.19; H, 11.30; N, 15.29.

Example 6 Example 7 1,3-di-(4-diezhylaminocyclohexyl) thiourea.A solution of 2.3 ml. (0.03 mole) of carbon disulfide in 4 cc. of methanol was added slowly to a cold solution of 2.0 g. (0.012 mole) of N,N-diethyl-1,4-cyclohexyldiamine in 20 ml. of methanol. As the addition progressed a solid separated. This suspension was heated under reflux for 2 days during which time solution was eifected. The reaction mixture was evaporated to dryness under reduced pressure, and the residue was recrystallized twice from ligroin (B.P. 90-100 C.), yielding 0.8 g. (35%), M.P. 164-165 C.

Analysis.-Calcd. for C H N S: C, 65.97; H, 11.00; N, 14.55; S, 8.36. Found: C, 65.80; H, 11.22; N, 14.74; S, 8.33.

Example 8 1 ,3-di- 4 -dielh ylam inocycloh ex'yl carbodiimide.-A mixture of 2.4 g. of mercuric oxide and 0.95 g. (2.5 mmoles) of 1,3-di-(4-diethylaminocyclohexyl) thiourea in 30 cc. of acetone was heated with stirring under reflux for 1 hour. The filtered reaction mixture was concentrated under reduced pressure and the residue was evaporatively distilled at C./0.03 mm., 0.575 g. (66% Analysis.Calcd. for C H N C, 72.36; H, 11.57; N, 16.08. Found: C, 72.25; H, 11.50; N, 16.34.

V a yellow oil, weight 1-2.8'g.

Example 9 .l-1cycl0heryI-3-( fl-diethylamindethyl) carbodiimide -A solution of 7:0 g. (0.05 -mole) of cyclohexylisothiocyanate [A.Skita and H. Rolfes, Ber., 53B, 1242 (1920)], and 5.8 g. (0.05 mole) of N,N-diethylethylene-*diamine in ether'was heated under reflux for 10 minutes. '-The ether iwas evaporated to dryness under reduced pressure, leaving A portion'ofthe thiourea (5 g.) was dissolvedin 75 ,cc. ofacetonecontaining 7.2 g. of mercuric oxide Merck yellow). The reaction solution was stirred and heated under reflux for 5 hours. The 'rnercuric sulfide was removed by filtration and an additional 7.0 g. t mercuric oxide was added followed by anovernight reflux period. After evaporation of the solvenhthe residual oilwas' purified by evaporation distillation at 100 C./0.- mm; yield,

Analysis-eCalcdiot C H N C, 69.90; H, 11:28;

Exqmple 1,0 I 1 ethyl-3 [Z-morph'olinyl (4.) -ethyll 1 thiourei- -lithylpholinyl-(4)-ethyll thioureaand 54.0 g. (0.25-mole) of ireshly dried mercuric oxidei(Merck-yelldw) in 500 ml. of dry acetone was stirred at room temperature for 12 hours. The mercuric sulfide-which formed was removed by filtration process was -repeated with two 27.0-g. pc fip s o me cu c x e the final m e n tr ated with activated carbon before filtration. The colorless filtrate was concentrated under reduced pressure to a. pale -9l1e 23, 2%).

Flash distilla 'on through a short-pathstill (oil bath 5504.0 4. m?) s e 2 0 0f o or s r a i id'a us 1- a E le 12 1 ethyl 3 [2 morpholinyl-M )-ethyl1 carbod'iimide merho-p-toluertesulfonateTA mixture of the basic carbodiimide (3.27 g.; 0.018 mole) and methyl p-toluenesul- 'fonate (3.32 g.;'0.018'mole) was heated withconstant swirling on a. steambath for 5 minutes. The-resulting viscous, orange oil was crystallized from acetone-benzene to 4.2 g, (64%) of colorless quaternary carbodiimide, M.P. 91.5-92.5 C.

' Example :13

1 ,-ethyl-3 [2-m rpholinyl-(4)-ethyll carb0diimide.- Two grams (0.0098 mole) of l-ethyl-3-i2 morpholinyli ..(4)ethyl]. urea (from ethyl isocya'nate and the amine) and 3.82 g. (0.02 mole) of p-toluenesulfonyl chloride were mixed slowly with 5.5 ml. pyridine .(reagent) in .20

' sodiumsulf ate and dried over sodium sulfate.

' The s h at w temb d-bywstm a at 21m H ml..dry methylene. chloride with stirringat 0 C. The

yield is, 25%. V

acrea Theresidual orange oil was distilled with N ebullition at mm, B.P. l00' 105 C., yield 0.37 g., 20% of the colorless product, l-ethyl 3 [2-morpholinyl-(4)-ethyll carbodiimide. g

" Example 14 I.-ethyl-3-[2-morpholinyl-(4)-ethyll carbodiimz'de hydrochloride-To a cooled (0-5 C.) solution of the basic carbodiimide, 1-ethyl-3-[2-rnorpholinyl-(4)-ethyl] carbodiimide (-3.2 7 g; 0.018 mole), in 20 .ml. of anhydrous ether was added slowly 0.017 mole of hydrogen chloride in 10 ml. of ether. After removal of solvent the watersoluble carbodiirnide salt, 1-ethyl-3 [2-morpholinyl (4)- ethyl] carbodiimide hydrochloride, is used without furthe: P ifi ati n V V 7 Example 15 1,3 di ('y 1 diethylqminopropyl) carbodiimide.-Five grams of -1,3-di-('y diethylaminopropyl) urea (from the corresponding amine and urea) and 9 g. of p-toluenesulfonyl chloride were mixed slowly with 12 ml. of pyridine and 60 ml. of dry methylene chloride with stirring at 0 C. After a reflux period of 6 hours the cooled solution was poured onto 60 g. of ice and7 g. of potassium carbonate. Additi onal potassium carbonate was added to maintain the pH at 8. The product was extracted with tour portions. of methylene chloride and the dried (sodiurnsulfate) extract was concentrated under reduced pressure. The 1,3-di-(7 -diethylaminopropyl) 7 carbod imide can be used without further purification. The

Example 17 1 ethyl-34 dimethylptminopropyl) carbodiimidez- Two grams of 1-ethyl-3-( y dimethylaminopropyl) urea (from ethyl isocyanate and N, N-dimethyl-1,3-propanediamine) and 3.5 g. of p-toluenesulfonyl chloride were added slowly to 5 ml. of pyridine in 30 ml. of dry methylene chloride with stirring at 0, C. After a 4-hour reflux periodthe-cooled solution was added slowly to a mixtureof 20 'g. of ice and 2 g. of sodium carbonate. Additional sodium carbonate was added tomaintain the pH of the solution at 8. The layers were'separated and the organic extract was dried over sodium sulfate and the solvent under reduced pressure. The 1-ethyl-3-( -dimethylaminopropyl) carbodiimide may be used directly or may be purified by distillation at 1 mm. The yield is 30%. 1

. Example 18 stirring and after 2 hours the solid, phthaloylglycylglycine ethyl ester, was collected, weight 0.18'g. (75%); M.P. 194-195" C. 7

The aqueous phasewas evaporated'a-t a temperature of 30 C. to remove water and leave a residue of the corresponding urea which was'regenerated into the carbcdiimide following the procedure of. Amiard, G. and

n /m s, R.,B1.1ll. Soc; Chirn. France, 1360 (1956).:

Example 19 Phthaloyl-L-threonine.T a solution of 4.54 g. (0.0306 mole) phthalic anhydride in 25 ml. of dry dioxane, there was added'3.04 g. (0.0255 mole) of L-threonine. The heterogeneous mixture was submerged in an oil bath at 105 C. and stirred vigorously for hours. After evaporation of the solvent under reduced pressure, the phthaloyl-L-threonine crystallized from acetonewater; yield, 6.0 g. (94%), M.P. 135-140 C. A portion of the product was recrystallized twice from ethanolwater, M.P. 143144 C., [111 D 36.7 (0.0480 g.

in 1.5 ml. absolute ethanol).

Analysis Calcd. for C H NO C, 57.80; H, 4.44; N, 561. Found: C, 58.06; H, 4.75; N, 5.54.

Phthaloyl-L-threonyl-L-phenylalanine methyl ester.- To a solution of 0.350 g. (0.0014 mole) of phthaloyl-L- threonine in 6 ml. of purified methylene chloride, there was added freshly prepared L-phenylalanine methyl ester (0.500 g., 0.0028 mole) (prepared by neutralizing an aqueous solution of L-phenylalanine methyl ester hydrochloride to pH 9.0 with potassium carbonate and subsequent extraction into ether; the hydrochloride was prepared by Fischer esterification) and N,N'-dicyclohexylcarbodiimide [13. Schmidt, F. I-Iitzler and E. Lahde, Ben, 71, 1933 (1938)] (0.290 g. 0.0014 mole). A precipitate of N,N-dicyclohexylurea formed immediately, but the reaction was allowed to proceed for 5 hours at room temperature.

The urea was removed by filtration and the methylene chloride solution was extracted successively with N hydrochloric acid, N potassium bicarbonate and water. After drying and subsequent removal of the solvent, the residue was crystallized from acetone-ether, yielding a total of 0.520 g. (91%) of product; M.P. 149-152 C. An analytical sample was obtained after two recrystallizations from acetone-ether, M.P. 153154 C., [1x1 D +1.93 (0.0986 g. in 1.5 ml. of dimethylformamide). Analysis.-Calcd. for C H N O C, 64.38; H, 5.40; N, 6.83. Found: C, 64.63; H, 5.65; N, 7.11.

Example 20 Phthaloyl-L-threonyl-L-Ieucine benzyl ester.To a solution of 0.600 g. (0.00241 mole) of phthaloyl-L-threonine in ml. of distilled acetonitrile, there was added L- leucine benzyl ester [prepared by neutralizing an aqueous solution of L-leucine benzyl ester hydrochloride to pH 9.0 with potassium carbonate and subsequent extraction into ether. The hydrochloride was synthesized according to the procedure of H. K. Miller and H. Waelsch, J. Am. Chem. Soc., 74, 1092 (1952)]. (0.810 g., 0.0036 mole) and N,N'-dicyclohexylcarbodiimide (0.495 g., 0.00241 mole).

The reaction was carried out as described for phthaloyl- L-threonyl-L-phenylalanine methyl ester. After the acetonitrile was removed by distillation under reduced pressure, the residue was taken up in ethyl acetate and extracted with acid, bicarbonate and water. After drying and removal of the solvent the residue was crystallized from acetonitrile-water yielding 0.980 g. (89%); M.P. 103-106 C. Two recrystallizations from acetone-etherhexane yielded an analytical sample; M.P. 109-110 C., [@126 D -16.7 (0.0770 g. in 1.5 ml. absolute ethanol).

AnaZysis.-Calcd. for C H N O C, 66.36; H, 6.24; N, 6.19. Found: C, 66.14; H, 6.25; N, 6.32.

Example 21 Phzhaloyl-L-threonyl-L-phenylalanine.-To a solution of 0.840 g. (0.00205 mole) of phthaloyl-L-threonyl-L- phenylalanine methyl ester in 30 ml. of acetone there was added 10 ml. of water and 5 ml. of concentrated hydrochloric acid. The solution was refluxed for two and a half hours and the acetone removed by distillation. Ethyl acetate was added and the product was subsequently ex- 10 tracted into bicarbonate solution. After acidification and re-extraction into ethyl acetate, drying and removal of the solvent under reduced pressure, the product was obtained as a crystalline mass. Recrystallization from ethanol-water yielded 0.510 g. (54%) of analytically pure material; M.P. 207-208 C., [M127 D +232 (0.025 g. in

. chloride was allowed to react as described for phthaloyl- L-threonyl-L-phenylalanine methyl ester.

The recrystallized product (ethanol-water) amounted to 0.245 g. (92%); M.P. 147.2-148 C.; [a] D ---25.6

(0.0271 g. in 1.5 ml. of absolute ethanol) Analysis.- Calcd. for C31H33N307I C, 66.77; H, 5.60; N, 7.54. Found: C, 66.71; H, 5.86; N, 7.48.

Example 22 ethanol). To a solution of 3.0 g. (0.0163 mole) of this product in ethanol there was added 162 g. (0.0160 mole) of tn'ethylamine. The resulting O-acetyl L-serine was recrystallized from water-ethanol, 2.42 g. (98%); d. 167- 168 C., [0:1 D =+9.15 (0.0268 g. in 1.5 ml. 0.1 N

hydrochloric acid).

Analysis.-Calcd. for C H NO C, 40.82; H, 6.12; N, 9.51. Found: C, 40.92; H, 6.41; N, 9.39.

Phthaloyl-O-acetyl-L-serine.T0 a solution of phthalic anhydride (2.0 g., 0.0135 mole) in 20 ml. of dry dioxane, there was added 1.65 g. (0.0112 mole) of O-acetyl-L- serine. The heterogeneous mixture was submerged in an oil bath'at C. and stirred vigorouslyfor 12 hours. The dioxane solution was lyophilized. The resulting oil was taken up in ether-chloroform mixture (3:1) and filtered. The solution was chromatographed on a g. silica gel column (Davison-Silica-gel, lot No. 923-08- 08-226, 100-200 mesh), previously washedwith ether, then with ether-chloroform (3:1). The crystalline product, 1.93 g. (63 emerged with the solvent front; M.P. -147 C. A portion of this material was recrystallized from ethanol-water for analysis; M.P. 151153 C., [0:1

D -63.1 (0.0363 g. in 1.5 ml. absolute ethanol).

0.0395 g. in 1.5 ml. of absolute ethanol).

Analysis.--Calcd. for CggHggNzOqZ C, 63.01; H, 5.06; N, 6.39. Found: c, 63.21; H, 5.34; N, 6.44.

Example 23 Carbobenzoxy-L-hydroxyprolyl-L-phenylalanine methyl ester.-A solution of carbobenzoxy-L-hydroxyproline II. S. Fruton, J. Biol. Chem, 146, .463 (1942)] (0.8 g.,

. melting point with g;,, 0.003 mole) in methylene chloride was treated as describedfor phth loyl-L-threonyl-L-phenylalanine meth yl ester. solution; yield, 1.1 g. (86%), M.P. 108-112 C. A portion of the material was recrystallized from acetone-etherhexane; M.P. 114-115 C., [1x1 D --29.2 (0.0416 g.

in 1.5 ml. absolute ethanol). I Analysis.-Calcd. for C2 H N Q C, 64.78; H, 6.10; N, 6.57., Found: C, 64.76; H, 6;36; N, 6.60.

f s Example 24 Phtlialoylglycylglycine ethyl ester-Run (a) .-To a suspension of 0.21 g. (1.46 mole) of glycine ethylester hydrochloride in 41:11. of "dry dioxane was added 0.38 g. (1.56 mole) of l-cyclyhexyl 3 [2 morpholinyl-(4)- ethyl] carbodiimide followed by 0.36 g. (1.46 mole) of phthaloylglycine. The mixture was stirred overnight after which the dioxane was distilled under reduced pressure. The residue was dissolved in ethyl acetate and this solution was washed first with 61111. of 1 N hydrochloric acid followed by 6 ml. of 1 N potassium bicarbonate. The ethyl acetate layer was dried over magnesium sulfate then evaporated to dryness. The residue, after crystallization from ethanol, weighed 033g. (80% M.P. 191-193" C. A mixed :melting point with authentic material was not depressed.

Run (b).The procedure given above was followed using a mixtureof 5 ml. of dioxane and 1 ml. of water as the solvent- .The other quantities were: 0.21 g. (1.46 mmole) of glycine ethyl ester hydrochloride, 0.43 g. (1.56 mmole) of N-cyclohexyl-N'-(4-diethylaminocyclohexyl) carbodiirnide and 0.3 g. (1.46 mmole).of phthaloylglycine. The product weighed 0.24 g. (83% R'u'n ('c).-To a solution of 0.18 g. (0.865 mmole) of phthaloylglycine and 0.088 g. (0.865 mmole) of glycine ethyl ester in 6 ml. of'water was added 0.4 g. (0.86 mmole) of the methyl p-tcluenesulfonate salt of N cyclo- (4 diethylaminecyelohexyl) carbodiimide. A solid began toseparate after 10 minutes of stirring and after 2 hours the solid was collected, weight 0.18 g. 75%); M.P. 194-195 c. 7

Run (d).--The procedure given in Run (a) was followed using 'dioxane as thesolvent, 24.7 mg. (0.29 mole) of glycine ethyl ester hydrochloride, 59.0 mg. (0.29 mmole) of phthaloylglyc'ine and 0.1 g. (0.29 mmole) of 1,3-di-(4-diethylaminocyclohexyl) carbo diiinide. The yield was 50 mg. (86%); M.P. 192-194 C.

- Example Y 1 .Phthaloyl L phenylalanylglycine ethyl ester-R un (a).--The experimental procedure described above for the preparation of phthaloylglycylglycine [Example 24, Run (a)] was followed using 0.196 g. (1.4 mmole) of glycine. ethyl ester hydrochloride, 0.4 g. (1.7 mmole) of N-cyclohexyl-N-['2-morpholinyl-(4)-ethyl] carbodiimide and 0.415 g. (1.4 nimole) ofphthaloyleL phenylalanine.

Recrystallization of the product from ethanol yielded 0:43 (81%); M.P. ISO-161 The product correspondedin rotation and an authentic sample [1. C. Sheehan, D. W. Chapmanand Roy W. Roth, J. Am. Chem. Soc., 74,3822 (1952)].

Run (b).To a solution of 0.196 g. (1.4 mmole) of glycine ethyl'ester hydrochloric and 0.41 g. (1.5 mmole) of N-cyclohexyl-N (4) diethylaminocyclohexyl carbodiimide in 6 ml. of dioxane was added, with stirring, 0.45. g. (1 .4 nmrole), ofphthaloyl-L-phenylalanine. The resulting reaction mixture was worked up as described above and afiordedOAQ-g. (90%); M.P. 16016l C.;

tised slp'agx nh' s nners or 2 811.- or water an s ml;

Crystallization occurred from an ethyl acetate C., [or 1 D -146 of dioxane as the solvent,- The product weighed 3.39 g. (71%); M.P. 160-161 (1., [0:] D 146 [ethanol].

Run. (d).'This experiment was carried out as described in Run (a) using dioxane, 0.196 g. (1.4 mmole) of glycine ethyl ester hydrochloride, 0.38 g. (1.7 mole) of N-cyclohexyl-N-(fi diethylaminoethyl) carbodiimide and 0.415 g. (1.4 mmole) of phthaloyl-L-phenyialanine. Recrystallization from ethanol yielded 0.11 g. (20%) of 0 product; M.P. 160161 C.; [0:] 2 --146 [ethanol].

7 Example'26. Phthaloyl-L-phenylalanyl-L-leucin-e ethyl ester-Run (a). The experimental procedure described for 5 'phthaloyl-L-glycylglycine ethyl ester [Run (a)] was followed using 0.27 g. (1.36 rnrnole) of L-leucine'ethyl ester hydrochloride, 5 ml. of dioxane, 0.39 g. (1.4 mmole) of N'-cyclohexyl-N-(4)-diethylaminocyclohexyl carbodiimide and 0.4 g. (1.36 mmole) of phthaloyl-L-phenyl- 0 alanine; yield,"0.5 g. (87%); M.P. 108 109 0.; [M

2 -115 [ethanol]. authentic sample did not show depression.

reaction mixture; yield, 50%.

The mixed melting point with an Example 27 30 above was followed using 0.12 g. (0.85 mrnole) of glycine M.P. 193-195 C.

ethyl ester hydrochloride, 3 ml. of dioxane, 0.24 g. (0.85 mmole) of 1-cyclohexyl-3-(4-diethylaminocyclohexyl) carbodiimide and 0.3 .g. (0.85 mmole) of carbobenzoxyglycyl-L-phenylalanine; yield, 0.3 g. (81%); M.P. l17 118 C.; [a] D l2.4 [ethanol] (reported: M.P.

l16118 C., [0:1 D 12).

" Example 28 Phthaloyl L ph'enylalanyl -'L phenylalanine methyl ester.-This reaction was carried out as described'previously using 0.216 g. (1.0 mmole) of L-phenylalanine methyl ester hydrochloride, dry dioxane, 0.285 g. (1.1 mmole) of N-cyclohexyl-N'-(4-diethylaminocyclohexyl) carbodiimide and 0.295 g. (1.0 mmole) r phthaloyl-L:

phenylalanine- The, product was crystallizedfrom an n.-butyl ether-hexane mixture;yield,g0.4 g. (88%,);Ml,v 10l-102 C.; [at] 2-428" [ethanol]. 7

A1mlysis." Calcd; for e n nt- 0s; c, 71.04; N; 5.30; N, 6.12. "Found: C, 70.75';'H, 5.54;N, 5.78. Example i Phenylacetzmilide' viwthe quatefhary carbodiimz'de, 1-

5 ethyl-3-[2-m0rph0linyl-(4)-ezhyl] carbodiimide methop-t0Zuenesulf0nate.- A solution'of 0.184 g. (1.35 mmoles) of phenylacetic acid, 0.126 g. (1.35 mmoles) of aniline, and 0.50"g; (1.35 mmoles) of quaternary carbodiimide, l -ethyl-3-[2-morpholinyl-(4)-ethyl] carbodiim-ide metho-' p-toluer esulfonate, in 25 ml. of purified methylene chloride was heated under reflux overnight. A'small quantity of'the urea which had separated was removed by:filtration (M.P.182-183) and the-filtrate washed successively with 10 ml. portions of water,'N hydrochloric acid, and N sodium bicarbonate. The dried (magnesium sulfate) solution was concentrated (aspirator). to; yield-0.-238 g. (83%) of phenylacetanilide, M.P. 116-118 .C. the product was recrystallized from benzene-petroleum ether (B.P. 30-60" C.) to give colorless needles melting at 7 benzene was added 0.50 g; (laminates srjm Example 30 Plienylactanilidvia dicyclohexylcarbolliimida l o a stirred solution of-0. 33 g; (2.42 mmole's bignes /nears acid -and'0.225 g. (2.42 mmoles) of-aniline in 25 inhef dicyclohexylcarbodiimide. The dicyclohexylurea formed in the reaction started to separate within a few seconds. After stirring overnight the urea was removed by filtration (M.P. 234.5235.5 C.) and the filtrate washed successively with ml. portions of N sodium bicarbonate and N hydrochloric acid. After drying over magnesium sulfate the solution was evaporated under reduced pressure. Crystallization of the residue from acetone-cyclohexane gave 0.357 g. (70%) of phenylacetanilide, M.P. 118.0-118.5 C.

Example 31 Example 32 Trifluoroacetanz'lide-A solution of 0.155 g. (1.35 mmoles) of trifluoroacetic acid, 0.126 g. 1.35 mmoles) of aniline, and 0.50 g. of the quaternary carbodiimide, 1-ethyl-3-[2-morpholinyl-(4)-ethyll carbodiimide methop-toluenesulfonate, in 25 ml. of purified methylene chloride was heated to reflux. After approximately 30 minutes the urea formed in the reaction started to separate. After 6 hours of reflux the mixture was cooled, the urea removed by filtration (M.P. 175178.5 C.), and the filtrate washed with 10 ml. of water and 10 ml. of N hydrochloric acid. From the organic layer there was obtained a crystalline residue which was crystallized again from iso-octane. The yield was 0.215 g. (85%), M.P. 90.5-91.0 C.

AnaZysis.--Calcd. for C H F NO: C, 51.07; H, 3.22. Found: C, 51.72; H, 3.45.

Example 33 Benzanilide.A solution of 0.165 g. 1.35 mmoles) of benzoic acid, 0.126 g. (1.35 mmoles) of aniline, and 0.50 g. (1.35 mmoles) of quaternary carbodiimide, 1-ethyl-3-[2-morpholinyl-(4)-ethyl] carbodiimide methop-toluenesulfon'ate, in ml. of purified methylene chloride was heated under reflux for 15 hours. The resulting colorless solution was washed with successive portions of water, N hydrochloric acid and N sodium bicarbonate, and then concentrated (aspirator) to a crystalline residue; 0.135 g. (51%), M.P. 164-165 C.

Example 34 N-l'2-morpholinyl-(4)-ethyl] phenylacetamide.-Aminoethylmorpholine (0.63 g.; 4.84 mmoles) was added to a solution of phenylacetic acid (0.66 g.; 4.84 mmoles) in 25 ml. of purified acetonitrile. In approximately 3 minutes the salt, morpholinoethylammonium phenylacetate, separated from solution. The mixture was heated (oil bath) with stirring to 50 C., at which temperature the salt redissolved. Dicyclohexylcarbodiimide (1.0 g.; 4.84 mmoles) was then added. Within 1 minute the dicyclohexylurea formed in the reaction started to separate from solution. Stirring was continued at this temperature for 13 hours. The urea was removed by filtration (M.P. 234236 C.) and the filtrate concentrated to a yellow oil. This was dissolved in 15 ml. of benzene and the solution extracted with three 10 m1. portions of N hydrochloric acid. Solid sodium bicarbonate was added to the aqueous extracts till basic (ca. pH 8) and the resultant solution extracted with three 25 ml. portions of methylene chloride. The dried organic layer was concentrated under reduced pressure to a partially crystalline residue. Crystallization from acetone-water gave 0.207 g. (58%) of the amide, M.P. 82.5-84" C. A sample recrystallized for analysis from acetone-water melted at 82.5-83.5 C.

Analysis.---Calcd. for C H N Q C, 67.71; H, 8.12. Found: C, 67.86; H, 8.29.

Example 35 N-cyclohexylphenylacetamide via the quaternary carbodiz'mide, 1-ethyl-3-[2-morpholinyl-(4)-ethyll carbodiimz'de metho-p-toluenesulf0nate.A solution of 0.203 g. (1.49 mmoles) of phenylacetic acid, 0.148 g. (1.49 mmoles) of cyclohexylamine, and 0.55 g. (1.49 mmoles) of quaternary carbodiimide, 1-ethyl-3-[2-morpholinyl- (4)-ethyl] carbodiimide metho-p-toluenesulfonate, in 50 ml. of purified methylene chloride was heated under reflux for 12 hours. The resulting colorless solution was concentrated (aspirator) to a volume of 20 ml. and

washed successively with 10 m1. portions of water, N

hydrochloric acid, and N sodium bicarbonate. The dried (magnesium sulfate) solution was concentrated under reduced pressure and the crystalline residue recrystallized from benzene-iso-octane. The yield was 0.10 g. (31%), M.P. 138.0-139.5 C.

Example 36 N-cyclohexylphenylacetamide via the basic carbodz imide, Z-ethyl-3-[2-m0rpholinyl (4) ethyl] carbadiimide.To a solution of 0.38 g. (2.79 mmoles) of phenylacetic acid in 50 m1. of purified methylene chloride was added 0.277 g. (2.79 mmoles) of cyclohexylamine. The salt, cyclohexylammonium phenylacetate, separated immediately. The basic carbodiim-ide, 1-ethyl-3-[2-morpholinyl-(4)-ethyll carbodiimide (0.512 g.; 2.79 mmoles) was added and the mixture heated under reflux for 9 hours. After an additional 48 hours at room temperature (stirring), the mixture was cooled and the unreacted salt removed by filtration mg.; 12%). The filtrate was concentrated (aspirator) to dryness and the residue extracted with benzene. An additional 55 mg. (8.5%) of unreacted salt remained. The benzene solution was washed successively with two 10 ml. portions of N hydrochloric acid and 10 ml. of sodium bicarbonate. The dried (magnesium sulfate) solution was concentrated under reduced pressure to a crystalline residue which was recrystallized from benzene-petroleum ether (B.P. 3060 C.) to give 0.150 g. (25%) of N-cyclohexylphenylacetamide, M.P. 137138 C.

Example 37 N-cyclohexylbenzamide via dicyclohexylearbodiimide in acet0ne.-Cyclohexylamine (0.24 g.; 2.42 mmoles) was added to a solution of benzoic acid (0.295 g.; 2.42 mmoles) in 25 ml. of acetone. The salt cyclohexylammonium benzoate separated immediately. Dicyclohexylcarbodiimide (0.50 g.; 2.42 mmoles) was added and the mixture stirred at room temperature for 13 hours. Nearly all of the material dissolved. The solvent was removed under reduced pressure. A benzene solution of the residue was concentrated gradually to give two crops, a total of 0.30 g. (38%), of N-benzoyl-N,N'- dicyclohexylurea, M.P. 166-167 C. A sample for analysis recrystallized from benzene-petroleum ether (B.P. 30-60 C.), melted at 1660-1665 C.

Analysis.-Calcd. for C H N O C, 73.13; H, 8.59. Found: C, 73.02; H, 8.68.

The combined filtrates (above) were washed successively with 5 ml. of N bicarbonate and two 5 ml. portions of N hydrochloric acid. Petroleum ether was added gradually to the dried (potassium carbonate) benzene solution. Anadditional 70 mg. (9%) of acylurea (colorless needles) and 69 mg. (14%) of N-cyclohexylbenzamide (platelets), M.P. 149-150 C., were isolated.

.15 V x l 6. 'N,-cy'clohexylbenzamide 'via the quaternary carbodi-i imidej I-ethyl-i- [ZQmorpholinyl-( l) -ethyl]- .carbodiimide iiietho-p toluenesulfnate.-A solution of. 0.334 g. (2.74 moles) of benzoic acid, 0.277 g. (2.79, mmoles) of cycloliexyla'mine, and 0.512 mmole) of the quaternary sulfate) solution wasv evaporated under re'duced pressure the crystalline residue recrystallijzed fromfbenlzene iso-octane. Theyield wasl50 mg. (9% ),of.N -oyclohexylregime m tin t 1 7- 4 r- 7 Example 39 V 7 To 4 ml. of a gelatin solutionat35? C(was. added in one portion 200 mg. of l-ethyl-3-[2:morpholinyl-(4I- ethyl] carbodiimide metho-p-toluenesulfonate. Within 30 seconds the solution; gelled; and did not reliquefy when heated to 95 C. r In. a. separate and similarexperiment the solution was allowed to stand overnight are; gelling at 25 'C., at which time the mixture had liquefied.

Various amounts of the carbodiimide were added at 35 C. to 5% gelatin solution at the isoelectric'point, pH: 5.1. After storing for 18 hours at 5 C(the melting point e de r -L Carbodiimide, Melting percentof gel weight: point, C. 0 '33;0' 2 33.0 5 34.9 10' 52.5

Slyke analysis yielded 0.19 nitrogen, while untreated gelatin yielded 0.64% nitrogen.

Example .43

A solution of 4.0 g. of gelatin'in 50 ml. of water was gelled by mixing with 2.25 g. of l-ethyl-3-[2-morpholinyl- (4)-ethyll carbodiimide metho-p-toluenesulfonate. The gel Was immediately freeze-dried, followed by trituration with 500 ml. of water. The resulting material after drying weighed 3.0 g. The wash water on evaporation yielded 2.3 g. of 1-ethyl-3 [2-morpholinyl-(4)-ethyll urea metho-p-toluenesulfonate. V

A 0.5 g. sample of the above-treated gelatin was dissolved in 20 ml. of a 50% calcium chloride solution by heating on a steam bath for 1 hour. A Sorensen titration,

' required 0.65 ml. of 0.103 N sodium hydroxide.

25 over 90.0

Example Phenylacataniilide via 1:ethyl-3-phenylcarbodiimideJ- To a solution of 0.33 g; of phenylacetic acid and 0.225 g. of anilinein 25 ml. purified methylenechloride was added 0.5 g. of 1-ethyl 3-phenylcarbodiimide. After storage for. 48 hours. at 25- C. there was isolated phenylacetanilide,

Maire-118 0.

Example 41 .Treatment of collagen with awater-sol tble .car bodiimz'de.--A'presoaked (in distilled water) fiber of kangaroo tail tendon was immersed for 24 hours 21 25 C(iri 10% aqueous solution of 1-ethyl=3-[2-morpholinyl- (4) ethyl] carbodiimide metho-p-toluenesulfonate.' V

The treated fiber shrank to a much less extent than did an untreated fiber when immersed in water at 90 C;

r g 7 Example 42 To a solution of 2.0 g. of gelatiuin 25.0 ml: of water was added 1.5 g. of 1-ethyl-3-[2-morpholinyl:( U-ethyl] carbodiirnide metho-p-toluenesulfonate. The solution gelled almost immediately (30 seconds), but liquefied on storage at room temperature for 16 hours. The resulting solution was dialyzed (using cellulose casing) for 4 days. T he solution was freeze-dried to a white powder; weight 2.0 g. A Sorensen titration (G.Wilson, Laboratory Manual of Physiological Chemistry}? The Williams and Wilkins Co., Baltimore, Md., 1952, p. 72), on 0.4 g. required 0.25 ml; of 0.103 N sodium hydroxide.

[Weith,B er., vs, 1530 1375 for'the introduction by injection or orally When 0.1 g. of the gelatin prepared above was suspended in 2.0 ml. of water containing 75 mg. of lethyl- 3-i2-morphclinyl-(4)-ethyl] urea metho-p-toluenesuh fonate, no liquefaction occurred even after 9 days. If,

I however, the carbodiimide was substituted for the urea,

liquefaction occurred.

When conductometric amino titrations [8. Ellis and I. Parkhurst, Biochem. J., 52, 350 (1952)], were carried out on the gelatin products of a decrease 111 ammo content as compared to untreated gelatin wasobserved.

Ex m e 4 'A solution of 0.2 g. of gelatin, 0.45 g; of urea and 0.15 g. of 1 -'ethyl-3-[2-morpholinyl (4)-ethyl] carbodiimide metho-p-toluenesulfonate.in 4.0 ml. of water gelled afte r 20 seconds. On. storage overnight the reaction mixture liquefied- V Example 45 To a solution of 0.1 g. of benzoyl gelatin in 2 ml. of water was added 0.1 g. of l-ethyl-3-[2-morpholinyl-(4)- ethyl] carbodiimide metho-p-toluenesulfonate. On stirring no sudden' gelation occurred as with the control gelatin. a V

J 7 Example 4 6- The liquefied, dialyzed, and then freeze-dried gelatin oi Example 42 was redissolved in water to produce a'5% solution. This solution was useful as a plasma substitute or blood plasma extender. It is devoid of amino acids other than those characteristic of gelatin. This new product permits the utilization of higher amino acid or protein content of gelatin in injectable, form without the dangerof gelation during or after injection. Thus, higher nutrient andlplasma simulating values are possessed by the, instant carbodiimide treated gelatin. Not only is this product a satisfactory substitute for blood plasma butjby. reason of the fact thatv it. may be safely introduced into the bodyinlarge quantities it, as well as the other gelatin, productsof this invention, may. be employed as a vehicle 'of'mariy medicines and foods, for example, antibiotics. (e.g., penicillins, tetracyclines), insulin, glucose, or protein hydrolysates'containing essential amino acids. The gelatin products of this. invention,.and of this example are useful in place ofthe oxypolygelatins as illustrated in Patents 2,591,133: and 2,811,482. 7 i v Example 47 The condensing action of carbodiimidesnpon gelatin to produce an insoluble gelatin is useful in the production of gelatin coated products having. tough exteriors, suitable as amend coatings, and preventing adhesion or, age

17 moved, quickly-washed with water, and-allowed to dry. The tablets were firm, non-tacky, with improved'struc- *tural strength, not readily disintegratable-in'water, but

readily soluble in" the intestine.

Example 48 Soft gelatin capsules containing vitamins .were passed through a 10% aqueous solution of l-ethyl-3-I2-morpholinyl-(4)-ethyll carbodiimide metho-prtoluenesulfonate, washed with water, and then dried. The capsules were non-adherent in the presence of atmospheric moisture and readily disintegrated upon oral administration. These capsules didnot requiretreatment with'lacquer to "Example 49 lnthe manufacture ofsoft gelatin capsules, thegelatin sheets were formulated with carbodiimide treatedgelatin .havinga melting point of about 50 .0, made as :described in Example :3 9, plasticized with glycerine. The resulting soft .capsules were moisture resistant.

Example 50 A 10% aqueous. solution of carbodiimide treated gelatin, prepared 'as'in Example '39, first-paragraph, was

whipped and aerated to a uniform foam and baked at 250 F. to dehydrate completely and sterilize the-product. The carbodiimide gelatin foam was useful as a surgical sponge. It had low-water disintegrabilityproperties'and remained uniform upon long storage. It was eventually absorbed by body fluids when enclosed in an animal body cavity.

. Example 51 A surgical sheep-gut suture was jimmersedin a 10% aqueous ,carbodiimide, l-ethyl-3-[2-rnorpholinyl-(4)- ethyl] carbodiimide 'methyl-p-toluene sulfonate solution for 6 hours, andwashed with water. It was found to be pliable but with -a higher tensile strength than originally possessed by the untreated suture material.

Example. 52

'A wet, developed photographic silver emulsionnegative film bearing a gelatin base emulsion on a celluloseacetate backing was dipped into a aqueous carbodiimide, :1- cyclohexyl 3-(4 diethylaminocyclohexyl) carbodiimide metho-p-toluenesulfonate, for 5 minutes, removed, and washed with Water. Even before drying, the hardening action upon the gelatin was noticeable. After drying, the hardness of the gelatin was prevailed in comparison with untreated gelatin emulsion films.

Example 53 Otherwise like Example 53, using a silk cloth sample in place of the woolen worsted produced an improved silk having good lustre and crease resistance.

18 Example '55 A fur felt was immersed for 24 hours in a S aqueous solution of l-cyclohexyl-S-(4-diethylaminocyclohexyl) carbodiimidemetho-p-toluenesulfonate, removed, washed .with water and dried. This felt showed improveddimensionalstability upon repeated wetting and drying as com- ..pared with untreated felt.

Example 56 The methods ofEXamples 53 and 55 were modified to the extent of employing a pretreatment of the polypep' tidematerial with 1% aqueouspapain for 6 hours at a pH of 7.5, or, alternatively, a pretreatmentwit-h trisodium phosphate at-pH. 12 for v6 hours, before the carbodiimide treatment described in Examples 53 and 55 wascarried out. These pretreatments were found especially effective.

flExample-ST Chicken body feathers were washed in water and curled by drying and drawing over sharply curved surfaces. The curled'feathers were treated with an organic :solution of N,N'-dicyclohexylcarbodiimide, 10% in benzene, in excess. The resulting feathersshowed increased water-repellency and improved flufliness retention.

Example 58 Fine womans hair, which had never beenpreviously waved, was washed, dried and then'wetted with a 5% aqueous solution of l-ethyl-3-[2-morpholinyl-(4)-ethyl] carbodiimide metho-p-toluenesulfonate, portions of the hair were wound on plastic mandrels, usingabsorbent 'endspaperaunder tension :and the -hair was permittednto the scope of the invention.

I claim: :1. in the formation of an'amideibyacondensing an amine having at leastone hydrogenatom attached to the .amino nitrogen, with an.organicicarboxylicsacideusing as the condensing agent a monocarbodiimide rhavingithe formula I RN=C=N--R, wherein each iRis .a monoxvalent: radical selected from-the group consisting of alkyl jradicals containing :from .2 to 12 carbon: atoms, :monoaryl-substituted lower alkyl radicals, di-lower alkylamino lower alkyl radicals, and morpholino 'piperidyland pyn'dyl-substituted lower alkyl radicals, and recover-ing the used condensing agent and the resulting amide condensation product.

2. The process of claim 1 wherein said monocarbodiimide is water-soluble.

3. The process of claim 1 amino acid.

4. The process of claim 1 wherein the organic carboxylic acid is an amino acid.

5. The process of claim 1 wherein at least one of the amide forming reactants is a peptide.

6. The process of claim 1 wherein at least one of the amide forming reactants is a protein.

7. The process of claim 1 wherein at least one of the amide forming reactants is collagen.

8. The process of claim .1 wherein both amide forming reactants are provided by a protein.

9. In the formation of an amide by condensing an amine, having at least one hydrogen atom attached to wherein the amine is an the amino-nitrogen, with an organic carboxylic acid claim-14. p 9

19 containing from 2 to 12 carbon atoms, monoaryl-substi tuted lower alkyl radicals, di-lower alkylamino lower alkyl radicals, and morpholino-, 'piperidyland pyr dylsubstituted lower alkyl radicals.

10. The method of preparing a modified gelatin comprising mixing, a water-soluble monooarbodiimide with an aqueous solution of gelatin and recovering the-modified gelatin from said solution, said monocarbodiimide having the formula R-N=C=N-R wherein each R is a monovalent radical selected from the group consisting of'alkyl radicals containing from 2 to 12 carbon atoms,

monoaryl-substituted lower alkyl radicals, di-lower alkylamino lower alkyl radicals, and morpholino-, piperidyland pyridyl-substituted lower alkyl radicalsg 11. The method ofprepariug a modified geIatin corn prising mixing a sufiicientproportion of a water-soluble mono'carbodiimide with an'aqueous solution of gelatin to produce a modified gelatin having its original amino. acid content but with a Van Slyke free amino-nitrogen analysis of less than about j95'percent'of the Van Slyke 1 free amino-nitrogen analysis of the corresponding untreated gelatin, said monocarbodiimide having the formula R-N='(FN- -R wherein each R is a 'monovalent radical selected from the group consisting of alkyl radicals'containing from 2 to 12. carbon atoms, monoaryl--.

content, but with a' Van Slyke free amino-nitrogen analysis of less than about 25 percent of the Van Slyke 'free amino-nitrogen analysis of the corresponding untreated gelatin, said 'monocarbodiimide having the for- --mula RN=C;NR wherein each R is a' monovalent radical selected from :the group consisting of alkyl radi-. --cals containing from 2' to 12 carbon atoms, monoarylsubstituted loweralkyl radicals; di-lower alkyl-amino lower alkyl radicals, and .Jmorpholino-, piperidyland' pyridyl-substituted lower alkyl radicals.

, '16. A modified gelatin freefrom added residues and -having a Van Slylge freearnino-nitrogenanalysis of less than about 95 percent of the Van Slykefree amino-nitrogen analysis of the corresponding untreated gelatin.

17. An aqueous dispersion of the modified gelatin of claim 16. 7 1,8,. In the formation of an amide by condensing an amine; having at least one hydrogen atom attached to the amino-nitrogen, with an organic 'carboxylic acid using a monocarbodiimide condensing agent, separating the used condensing agent from the resulting amide condensation product, regenerating the used condensing agent to produce more monocarbodiimide and recycling 0 the monocarbodiimide to efiect additional formation of 13. A modified gelatin characterized by theproperty of having aisubstantial proportion of its free carboxyl groups condensed with asubstantialproportion of its free amino groups.

14; A modified gelatin free from added residues and having a melting point of at leastS C. greater than the corresponding unmodified gelatin and an acylated lysine I e-amino content of at least about 5 percent. a g

15. An aqueous dispersion of the modified gelatin of 'amide, said monocarbodiimide having the .formula R N=C;=NR wherein each R is a monovale'nt radic'al jselected' from ithe groupi consisting of alkyl radicals containing from '2 to 12carbon atoms, monoaryl-substituted. lower alkyl' radicals, di-lower' alkyl-amino lower alkyl radicals, and morpholino-{piperidyland pyridylsubstituted lower alkyl radicals.

19. In the formation of an amide by condensing an amine, having at least one hydrogen atom attached to the amino-nitrogen, with an organic carboxylic acid using as the condensing agent an'aqueous solution of a watersoluble monocarbodiirnide, separating the spent watersoluble monocarbodiimide from the condensation product,-regenerating the monocarbodiimide and recycling the regenerated monocarbodiimide to efiect additional formation of amide, said monocarbodiimide having the formula RN=O=N-R wherein each R is a mono valent radical selected from the group consisting of alkyl radicals containing from 2to 12 carbon atoms, monoaryl-substituted lower alkyl radicals, di-lower alkylamino lower alkyl radicals, and morpholino-, piperidyland pyridyl-substituted lower alkyl radicals. 20. Theprocess of claim 1 wherein both amide forming reactants are provided by an amino acid. V 21, ;The process of claiml wherein at least one of the amide forming reactants is a protein fiber.

22. 'In the formation of amide by condensing an amine having at least one hydrogen atom attached to the amino nitrogen, with ganorganic carboxylic acid using the condensing agent, l-ethYl-S-phenylcarbodiimide.

; I References Cited inlthe file of this patent V -UNITED STATES PATENTS 2,284,896 I Hartford et'al; June 2, 1942 2,786,049 Lundgren et al. Mar. 19,1957 2,793,204 Arens May 21, '1957 2,850,496 Hardman Sept. 2, 1958 Math et a1. June 16, 1959 

1. IN THE FORMATION OF AN AMIDE BY CONDENSING AN AMINE HAVING AT LEAST ONE HYDROGEN ATOM ATTACHED TO THE AMINO NITROGEN, WITH AN ORGANIC CARBOXYLIC ACID USING AS THE CONDENSING AGENT A MONOCARBODIIMIDE HAVING THE FORMULA R-N=C=N-R, WHEREIN EACH R IS A MONOVALENT RADICAL SELECTED FROM THE GROUP CONSISTING OF ALKYL RADICALS CONTAINING FROM 2 TO 12 CARBON ATOMS, MONOARYL-SUBSTITUTED LOWER ALKYL RADICALS, DI-LOWER ALKYLAMINO LOWER ALKYL RADICALS, AND MORPHOLINO-, PIPERIDYL- AND PYRIDYL-SUBSTITUTED LOWER ALKYL RADICALS, AND RECOVERING THE USED CONDENSING AGENT AND THE RESULTING AMIDE CONDENSATION PRODUCT.
 8. THE PROCESS OF CLAIM 1 WHEREIN BOTH AMIDE FORMING REACTANTS ARE PROVIDED BY A PROTEIN. 